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An Introduction to Reamers & CNC Reaming

Most machinists are familiar with CNC drilling, but did you know that the common practice for holemaking is to always use a reamer? When done correctly, reaming can be a fast and highly accurate operation that results in precision holes.

Critical Reamer Geometries

reamers

By examining a Harvey Tool Miniature Reamer and its critical dimensions, we can better understand the functionality of this useful tool. In the above image of a straight flute reamer, D1 references the reamer diameter, the specific size intended for your hole; and D2 points to the shank diameter. At Harvey Tool, reamer shanks are oversized to help maintain tool strength, stiffness, and accuracy. Shanks also have an h6 tolerance, which is crucial for high precision tool holders, such as heat shrink collets. Other critical dimensions of a reamer include its overall length (L1), margin length (L2), overall reach (L3), and chamfer length (L4).

Harvey Tool also offers Miniature Reamers – Right Hand Spiral. This tool is designed to leave a superior part finish and help with chip evacuation in blind hole applications.

The Functions of Miniature Reamers

Reamers Provide Precision – As mentioned earlier, reamers are great for machining precision hole diameters. To use a reamer properly, you must first have a pre-drilled hole that’s between 90% and 94% of the final hole diameter. For example, if you need a finished a hole of .220″, your predrilled hole should be somewhere between .1980″ and .2068″. This allows the tool to take enough material off to leave a great finish, but does not overwork it, potentially causing damage. The tolerance for uncoated reamers is +.0000″/-.0002″, while the tolerance for AlTiN coating is +.0002″/-.0000″. These tolerances provide you the peace of mind of knowing that your hole will meet exact specifications.

Achieve a Quality CNC Finish – When a high surface finish is required of a hole, reamers should always be used to reach the desired tolerance. Both the pre-drilled hole and the tool’s margin help to keep the reamer centered while cutting, leading to a better finish.

Minimize Machining Production Runs – For machine shops, consistency is a priority. This is especially true in production runs. The last thing a machinist wants to see is an oversized hole on a part they have already preformed many operations on. Remember, reamers have the benefit of offering consistent hole size, preventing an out of tolerance finish. These consistent holes lead to valuable time savings and reduced scrap costs.

CNC Machining Exotic Alloys: When machining Inconel, titanium, and other high-cost materials, reaming your hole is important to ensure that the desired finish specification is met. With reamers, a machinists can better predict tool life, leading to a better finished product and less scrap ratios. It is important to note that Harvey Tool reamers are offered AlTiN coated and fully stocked in every .0005” increment from .0080” to .0640”.

Drill / End Mills: Drill Style vs. Mill Style

Drill / End Mills are one of the most versatile tools in a machinist’s arsenal. These tools can perform a number of different operations, freeing space on your carousel and improving cycle times by limiting the need for tool changes. These operations include:

  1. Drilling
  2. V-Grooving
  3. Milling
  4. Spot Drilling
  5. Chamfering

The ability of the Drill / End Mill to cut along the angled tip as well as the outer diameter gives it the range of operations seen above and makes it an excellent multi-functional tool.

drill mill operations

Drill Style vs. Mill Style

The main difference between Drill / End Mill styles is the point geometry.  They are defined by how the flutes are designed on the end of the tool, using geometry typically seen on either an end mill or a drill.  While mill style tools follow the features of an end mill or chamfer mill, the drill style geometry uses an S-gash at the tip.  This lends strength to the tip of the tool, while giving it the ability to efficiently and accurately penetrate material axially.  While both styles are capable of OD milling, mill style tools will be better for chamfering operations, while drill style will excel in drilling.  The additional option of the Harvey Tool spiral tipped Drill / End Mill is an unprecedented design in the industry.  This tool combines end geometry taken from our helical flute chamfer cutters with a variable helix on the OD for enhanced performance. Versatility without sacrificing finish and optimal performance is the result.

drill mills

Left to Right: 2 Flute Drill Style End, 2 Flute Mill Style End, 4 Flute Mill Style End

Drill Mills: Tool Offering

Harvey Tool currently offers Drill / End Mills in a variety of styles that can perform in different combinations of machining applications:

Mill Style – 2 Flute

This tool is designed for chamfering, milling, drilling non-ferrous materials, and light duty spotting. Drilling and spotting operations are recommended only for tools with an included angle greater than 60°. This is a general rule for all drill mills with a 60° point. Harvey Tool stocks five different angles of 2 flute mill-style Drill / End Mills, which include 60°, 82°, 90°, 100° and 120°. They are offered with an AlTiN coating on all sizes as well as a TiB2 coating for cutting aluminum with a 60° and 90° angle.

drill mill

Mill Style – 4 Flute

4 flute mill-style Drill / End Mills have two flutes that come to center and two flutes that are cut back. This Drill / End Mill is designed for the same operations as the 2 flute style, but has a larger core in addition the higher flute count. The larger core gives the tool more strength and allows it to machine a harder range of materials. The additional flutes create more points of contact when machining, leading to better surface finish. AlTiN coating is offered on all 5 available angles (60°, 82°, 90°, 100°, and 120°) of this tool for great performance in a wide array of ferrous materials.

drill mill

Drill Style – 2 Flute

This tool is specifically designed for the combination of milling, drilling, spotting and light duty chamfering applications in ferrous and non-ferrous materials. This line is offered with a 90°, 120°, and 140° included angle as well as AlTiN coating.

drill mills drill style

Helical Tip – 4 Flute

The Helically Tipped Drill / End Mill offers superior performance in chamfering, milling and light duty spotting operations. The spiral tip design allows for exceptional chip evacuation and surface finish. This combined with an OD variable helix design to reduce chatter and harmonics makes this a valuable tool in any machine shop. It is offered in 60°, 90°, and 120° included angles and comes standard with the latest generation AlTiN Nano coating that offers superior hardness and heat resistance.

 

Selecting the Right Harvey Tool Miniature Drill

Among Harvey Tool’s expansive holemaking solutions product offering are several different types of miniature tooling options and their complements. Options range from Miniature Spotting Drills to Miniature High Performance Drills – Deep Hole – Coolant Through. But which tools are appropriate for the hole you aim to leave in your part? Which tool might your current carousel be missing, leaving efficiency and performance behind? Understanding how to properly fill your tool repertoire for your desired holemaking result is the first step toward achieving success.

Pre-Drilling Considerations

Miniature Spotting Drills

Depending on the depth of your desired machined hole and its tolerance mandates, as well as the surface of the machine you will be drilling, opting first for a Miniature Spotting Drill might be beneficial. This tool pinpoints the exact location of a hole to prevent common deep-hole drilling mishaps such as walking, or straying from a desired path. It can also help to promote accuracy in instances where there is an uneven part surface for first contact. Some machinists even use Spotting Drills to leave a chamfer on the top of a pre-drilled hole. For extremely irregular surfaces, however, such as the side of a cylinder or an inclined plane, a Flat Bottom Drill or Flat Bottom Counterbore may be needed to lessen these irregularities prior to the drilling process.

spotting drill

Tech Tip: When spotting a hole, the spot angle should be equal to or wider than the angle of your chosen miniature drill. Simply, the miniature drill tip should contact the part before its flute face does.

spotting drill correct angle

Selecting the Right Miniature Drill

Harvey Tool stocks several different types of miniature drills, but which option is right for you, and how does each drill differ in geometry?

Miniature Drills

Harvey Tool Miniature Drills are popular for machinists seeking flexibility and versatility with their holemaking operation. Because this line of tooling is offered uncoated in sizes as small as .002” in diameter, machinists no longer need to compromise on precision to reach very micro sizes. Also, this line of tooling is designed for use in several different materials where specificity is not required.

miniature drill

Miniature High Performance Drills – Deep Hole – Coolant Through

For situations in which chip evacuation may be difficult due to the drill depth, Harvey Tool’s Deep Hole – Coolant Through Miniature Drills might be your best option. The coolant delivery from the drill tip will help to flush chips from within a hole, and prevent heeling on the hole’s sides, even at depths up to 20 multiples of the drill diameter.

miniature drill coolant through

Miniature High Performance Drills – Flat Bottom

Choose Miniature High Performance Flat Bottom Drills when drilling on inclined and rounded surfaces, or when aiming to leave a flat bottom on your hole. Also, when drilling intersecting holes, half holes, shoulders, or thin plates, its flat bottom tool geometry helps to promote accuracy and a clean finish.

flat bottom drill

Miniature High Performance Drills – Aluminum Alloys

The line of High Performance Drills for Aluminum Alloys feature TiB2 coating, which has an extremely low affinity to Aluminum and thus will fend off built-up edge. Its special 3 flute design allows for maximum chip flow, hole accuracy, finish, and elevated speeds and feeds parameters in this easy-to-machine material.

drill for aluminum

 

Miniature High Performance Drills – Hardened Steels

Miniature High Performance Drills – Hardened Steels features a specialized flute shape for improved chip evacuation and maximum rigidity. Additionally, each drill is coated in AlTiN Nano coating for hardness, and heat resistance in materials 48 Rc to 68 Rc.

drill for hardened steel

Miniature High Performance Drills – Prehardened Steels

As temperatures rise during machining, the AlTiN coating featured on Harvey Tool’s Miniature High Performance Drills – Prehardened Steels creates an aluminum oxide layer which helps to reduce thermal conductivity of the tool and helps to promote heat transfer to the chip, as well as improve lubricity and heat resistance in ferrous materials.

drill for prehardened steel

Post-Drilling Considerations

Miniature Reamers

For many operations, drilling the actual hole is only the beginning of the job. Some parts may require an ultra-tight tolerance, for which a Miniature Reamer (tolerances of +.0000″/-.0002″ for uncoated and +.0002″/-.0000″ for AlTiN Coated) can be used to bring a hole to size. miniature reamer

Tech Tip: In order to maintain appropriate stock removal amounts based on the reamer size, a hole should be pre-drilled at a diameter that is 90-94 percent of the finished reamed hole diameter.

Flat Bottom Counterbores

Other operations may require a hole with a flat bottom to allow for a superior connection with another part. Flat Bottom Counterbores leave a flat profile and straighten misaligned holes. For more information on why to use a Flat Bottom Counterbore, read 10 Reasons to Use Flat Bottom Tools.

flat bottom counterbores

Key Next Steps

Now that you’re familiar with miniature drills and complementary holemaking tooling, you must now learn key ways to go about the job. Understanding the importance of pecking cycles, and using the correct approach, is vital for both the life of your tool and the end result on your part. Read this post’s complement “Choosing the Right Pecking Cycle Approach,” for more information on the approach that’s best for your application.

Choosing The Right Pecking Cycle Approach

Utilizing a proper pecking cycle strategy when drilling is important to both the life of your tool and its performance in your part. Recommended pecking cycles vary depending on the drill being used, the material you’re machining, and your desired final product.

What are Pecking Cycles?

Rather than drill to full drill depth in one single plunge, pecking cycles involve several passes – a little at a time. Pecking aids the chip evacuation process, helps support tool accuracy while minimizing walking, prevents chip packing and breakage, and results in a better all around final part.

Recommended Pecking Cycles / Steps

Miniature Drills

miniature drill pecking cycles

High Performance Drills – Flat Bottom

pecking cycles

High Performance Drills – Aluminum & Aluminum Alloys

aluminum pecking cycles

Note: For hole depths 12x or greater, a pilot hole of up to 1.5X Diameter is recommended.

High Performance Drills – Hardened Steels

hardened steels pecking cycles
High Performance Drills – Prehardened Steels

prehardened steels pecking cycles

Key Pecking Cycle Takeaways

From the above tables, it’s easy to identify how recommended pecking cycles change based on the properties of the material being machined. Unsurprisingly, the harder the material is, the shorter the recommended pecking depths are. As always, miniature drills with a diameter of less than .010″ are extremely fragile and require special precautions to avoid immediate failure. For help with your specific job, contact the Harvey Tool Technical Team at 800-645-5609 or [email protected]

Multi-Functional Tools Every Shop Should Have

If there is one thing that all machinists and shop managers can agree on, it’s that time is money. Tool and material costs, employee wages, and keeping the lights on all add up, but most would agree that saving time is one of the best ways to make a shop more efficient.

Tool changes mid-job quickly add up when it comes to cycle times (not to mention tool costs), so using a tool capable of multiple operations whenever possible is an excellent first step. The following multi-functional tools are designed to save time and money at the spindle.

Drill/End Mills

drill mills

One look at Drill/End Mills or “Drill Mills” and it’s obvious that these tools are capable of more than a standard end mill. Two of the intended operations are right in the name (drilling and milling). Besides the obvious, though, drill mills are intended for grooving, spotting, and chamfering, bringing the total to five separate operations.

drill mill operations

Considering the amount of tools normally required to perform all of these common operations, keeping a few drill mills in your tool crib ensures you’re always ready to tackle them, not to mention the potential extra spots in your tool magazine.

Undercutting End Mills

undercutting end mills

Undercutting End Mills, also known as lollipop cutters or spherical ball end mills are surprisingly “well-rounded” tools. Besides milling an undercut feature on a part, which is typically very difficult with a standard end mill, these tools are capable of a few other operations.

undercutting end mill operations

Using an undercutting end mill to deburr in your machine is an excellent way to save time and effort. Some slotting and contouring operations, especially when 5-axis milling, are made far easier with an undercutting end mill, and in some situations, clearance challenges make them necessary.

Double Angle Shank Cutters

double angle shank cutters

Often referred to the “Swiss Army Knife of Machining” due to their versatility, Double Angle Shank Cutters are 6-in1 tools worth keeping on hand in any machine shop. Since these tools cut on all sides of their head, they are useful in a variety of situations.

multi-functional tools

With the ability to thread mill and countersink, Double Angle Shank cutters are perfect for holemaking operations. On top of that, their clearance advantage over standard end mills makes them extremely well suited to a variety of finishing operations in difficult to reach places.

Flat Bottom Tools

flat bottom tools

Flat Bottom Drills and Flat Bottom Counterbores are better suited to holemaking, but they are capable of a large variety of operations. They belong in a category together since their flat bottom geometry is what sets them apart from other tools in the same category. Flat bottom geometry keeps the tool from walking on irregular or angle surfaces and help to correct, straighten, or flatten features created by non-flat bottom tools.

Flat bottom drills are designed for the following operations:

multi-functional tools

While similar in some aspects, flat bottom counterbores are particularly well-suited for these uses:

flat bottom tools

Adjustable Chamfer Cutters

adjustable chamfer cutters

As discussed in a previous post, chamfer mills are capable of more than just chamfering – they are also well-suited for beveling, deburring, spotting, and countersinking. However, these adjustable chamfer cutters aren’t limited to a single angle per side – with a quick adjustment to the carbide insert you can mill any angle from 10° to 80°.

chamfer cutter inserts

When you account for the replaceable insert and the range of angles, this tool has a very high potential for time and tool cost savings.

Tools that are capable of a variety of operations are useful to just about any machine shop. Keeping your tool crib stocked with some or all of these multi-functional tools greatly increases your shop’s flexibility and decreases the chances of being unprepared for a job.

10 Reasons to Use Flat Bottom Tools

Flat bottom tools, or tools with flat bottom geometry, are useful in a variety of a situations and operations that tools with typical cutting geometry are not. The standard characteristics of drills or end mills are useful for their primary functions, but make them unsuitable for certain purposes. When used correctly, the following flat bottom tools can make the difference between botched jobs and perfect parts.

Flat Bottom Drills

Flat Bottom Drill

Flat bottom drills are perfect for tricky drilling situations or for creating flat bottom holes without secondary finishing passes. Consider using these specialized drills for the operations below.

 

Flat Bottom Drill Operations

Thin Plate Drilling

When drilling through holes in thin plates, pointed drills are likely to push some material out the exit hole and create underside burrs. Flat bottom drills are significantly less likely to experience this problem, as their flat bottom geometry generates more even downward forces.

Crosshole Drilling

When drilling a hole that crosses the path of another hole, it is important to avoid creating burrs, since they can be extremely difficult to remove in this kind of cross section. Unlike drills with points, flat bottom drills are designed to not create burrs on the other side of through holes.

Irregular/Rounded Surface Drilling

Flat bottom drills initially engage irregular surfaces with their outer edge. Compared to making first contact with a standard drill point, this makes them less susceptible to deflection or “walking” on inclined surfaces, and more capable of drilling straighter holes.

Angled Drilling

Even if the surface of a part is flat or regular, a pointed drill is susceptible to walking if it engages the part at an angle, known as angled or tilted drilling. For the same reason flat bottom drills are ideal for drilling on irregular surfaces, they are perfect for angled drilling.

Half Hole Drilling

When drilling a half hole on the edge of a part, the lack of material on either side of the drill makes the operation unstable In this situation, a pointed drill is susceptible to walking. A flat bottom drill makes contact with its entire cutting geometry, allowing for more versatility and stability when drilling half holes.

 

Flat Bottom Counterbores

Flat Bottom Counterbore

Flat bottom counterbores are an excellent choice when a flat bottom hole is needed and a tool without flat bottom geometry was used to create it. Keep some of these tools on hand to be prepared for the operations below.

 

Flat Bottom Counterbore Operations

Bore & Finish Drilled Holes

Drill geometry is designed first and foremost for factors like stability, rigidity, and chip evacuation. Some holes will need secondary finishing operations. Flat bottom counterbores are often designed with a slow helix and low rake, which help them avoid part engagement and control finish.

Straighten Misaligned Holes

Even experienced machinists may drill a less-than-perfectly-straight hole or two in new and unfamiliar jobs. Fortunately, flat bottom counterbores are well-suited for straightening misaligned holes.

Spot Face & Counterbore on Irregular Surfaces

The unique geometry of flat bottom counterbores makes them  effective at spotting on irregular surfaces. Standard drills and spot drills are susceptible to walking on these kinds of surfaces, which can potentially ruin an operation.

Remove Drill Points

When a standard drill creates a hole (other than a through hole) it leaves a “drill point” at the bottom due to its pointed geometry. This is fine for some holes, but holes in need of a flat bottom will need a secondary operation from a flat bottom counterbore to remove the drill point.

Remove End Mill Dish

The dish angle present on most standard end mills allows proper end cutting characteristics and reduces full diameter contact. However, these end mills will naturally leave a small dish at the bottom of a hole created by a plunging operation. As with drill points, flat bottom counterbores are perfect to even out the bottom of a hole.